Separation of fatty materials



United States Patent US. Cl. 260-419 14 Claims ABSTRACT OF THEDISCLOSURE A method is provided for separating mixtures of fattymaterials. In the method the mixture of fatty material is formed at atemperature at which the mixture is substantially fluid. The mixture isthereafter cooled by placing the mixture under vacuum conditions andevaporating a lower boiling fluid in the presence of the fattymaterials. The conditions are selected so as to establish a temperaturein the mixture wherein at least a part of the mixture forms a solidphase. The liquid portion of the mixture is then emulsified with anaqueous solution of a surface active material by adding the solution tothe mixture. The liquid portion of the fatty materials emulsified in theaqueous solution is thereafter separated with it from the solid phase byany suitable solid-liquid separation technique, such as filtration orcentrifugation.

This invention relates generally to a method for separation of fattymaterials, and more particularly it relates to the separation ofmixtures of fatty materials or their derivatives.

Fatty materials, such as fatty acids and triglyceride oils, are usuallyobtained from natural or synthetic sources as a mixture of componentswhich differ from one another by their melting points. It is sometimesdesirable to separate these mixtures into components. For example, fattyacids derived from tallow may be separated into a stearic acid fractionand an oleic acid fraction.

One known process for separating fatty acids derived from tallow is by apressing operation. In such process, the mixture of fatty acids obtainedfrom tallow is subjected to successive pressing operations attemperature such that at least part of the mixture is solid. Thesaturated fatty acids, such as palmitic and stearic acids, solidifyfirstand are recovered as a solid fraction. The solid fraction obtained frompressing tallow is known as commercial stearic acid. The liquid fractionwhich is removed by the pressing contains primarily unsaturated fattyacids, principally oleic acid and is known as red oil. Separation offatty acids by pressing is slow and gives poor recovery of the separatecomponents of tallow.

To improve quality, the solids are sometimes given an additionalpressing at higher temperatures to remove more of the liquid unsaturatedfatty acid and produce a material known as double or triple pressedstearic acid. The above-described pressing method for separating fattyacids is subject to numerous disadvantages, including low quality of thecomponents obtained, inetfic'ient operation, and slow and costlyprocedures.

Separation of fatty acids into solid and liquid components has also beeneffected by the use of solvents and by the formation of emulsions andsubsequent centrifugation. These other known prior art methods forseparating fatty acids are also subject to disadvantages in that asolvent recovery step must be elfected, or that costly centrifugalseparation equipment must be utilized.

Centrifugal separation has been found to be essential in various priorart methods due to the type of solid phase crystals that is formed whena mixture of fatty ice acids is cooled rapidly. It would be desirable toprovide an improved method for the separation of mixtures of fatty acidswherein cooling of a fluid mixture of fatty acids may be effectedrapidly and still provide solid phase crystals that are readilyseparated from the liquid phase.

It would also be desirable to provide an improved process by whichhigher-melting glycerides can be removed from glyceride oils. A processfor accomplishing this is generally referred to as winterization of theglyceride oil. Separation of such higher-melting glycerides was formerlycarried out simply by allowing the glyceride oil to stand and settle outin outside tanks during the winter. The process is now carried outinside with mechanical refrigeration, but substantial improvement in thetime required for separation of the higher-melting glycerides has notimproved.

Winterized edible glyceride oils that will be substantially free of hardfat crystals at temperatures of 40 F. are required for use in productskept in household refrigerators. The problem in Winterizing oil isprimarily a matter of providing crystals in a form that can be separatedfrom the uncrystallized liquid oil. In normal practice, the oil must becooled slowly over a period of several days to produce filterablecrystals, and even under the most favorable circumstances, the finalseparation of solid, higher-melting glycerides and liquid oil isdiflicult and incomplete. Because the operation of winterization is slowand better separations are desired, winterization is not a particularlysatisfactory oil processing method. It would be desirable to provide animproved method for Winterizing liquid glyceride oils.

Accordingly, it is an object of the present invention to provide animproved method for separating fatty materials. Another object of thepresent invention is to pro vide a method for separating mixtures offatty materials into components without the necessity of using organicsolvents or centrifugal separation equipment. It is another object ofthe present invention to provide an improved method for the separationof fatty acid mixtures. It is a further object of the present inventionto provide an improved method for the separation of high-meltingglycerides from glyceride oils. It is a still further object of thepresent invention to provide an improved method for separating mixturesof fatty esters into components of different melting points. I

These and other objects of the present invention will become moreapparent from the following detailed description and the drawing, whichis a schematic diagram of a flow sheet embodying various of the featuresof the present invention.

In accordance with various of the features of the present invention, amixture of fatty materials is formed at a temperature at which themixture is substantially fluid. The mixture will include fatty materialshaving fatty acid residues with carbon chain lengths greater than 10 andmay comprise glyceride materials, fatty acids or esters. The mixture isthereafter cooled by placing the mixture under vacuum conditions andevaporating a lower boiling fluid in the presence of the fattymaterials. The lower boiling fluid may or may not be in admixture withthe fatty materials. The cooling conditions are selected to establish atemperature in the mixture so that at least a part of the mixture formsa solid phase. The liquid portion of the mixture is then emulsified withan aqueous solution of a surface active material by adding the solutionto the mixture. The liquid emulsion of fatty materials and the aqueoussolution is thereafter separated from the solid phase by any suitablesolid-liquid separation technique, such as filtration or centrifugation.

The method of the present invention is particularly suitable forseparating mixtures of fatty acid esters or 3 fatty acids of bothnatural and synthetic origin and certain features of the invention willhereafter be described with reference to such mixtures.

Fatty acid esters, particularly glycerides, are usually obtained fromthe fat of vegetables and from land and marine animals. Examples of thevarious vegetable fats suitable for separation by the method of thepresent invention are coconut oil, rapeseed oil, soy bean oil,cottonseed oil, peanut oil, linseed oil, palm oil and olive oil. Animalfats include beef fat, particularly tallow, and hog fat. Marine fatsinclude those obtained from whale oil, menhaden oil, codliver oil andherring oil. Fatty acid esters which contain alcohols other thanglycerin as the alcohol component may also be processed by the method ofthe present invention.

Fatty acid mixtures are usually obtained from the naturally occurringfats mentioned above. The esters may be split with the aid of water orsteam or may be saponifled with the aid of caustic after which the fattyacids are liberated from the resulting soaps with the aid of acids.Fatty acid mixtures may also be obtained by the oxidation of natural orsynthetic paraffin or the oxidation of alcohol.

The invention is, however, not limited to any specific enumeratedmixture of fatty acids or fatty acid esters, but is rather applicable toall similar mixtures regardless of the source or procedure for obtainingsuch mixtures.

The mixture of fatty materials to be separated is preferably heated to atemperature such that the higher melting of the components of themixture substantially loses its crystal structure. However, it is notnecessary to heat the mixture to a temperature wherein each of thecomponents of the mixture is completely melted. For example, where amixture of stearic acid and oleic acid is to be separated, the mixtureof acids is preferably heated to a temperature of at least about 90 F.,but does not have to be heated to a temperature in excess of 120 F. atwhich temperature the stearic acid is substantially melted.

After the mixture of fatty materials has been heated to the desiredtemperature, the mixture is transferred to a chamber which is equippedto draw vacuum therein. Vacuum equipment is provided for establishing avacuum sufficient to effect desired cooling under the conditions of thesystem. It will be readily understood from the further detaileddescription of the cooling process of the invention that the rate ofcooling is dependent on the level and capacity of vacuum, i.e., thelower the absolute pressure the more rapid the rate of cooling will beto the extent that the vacuum producing means is capable of withdrawingthe evaporated fluid. The rate of cooling is also related to the rate ofevaporation of the lower boiling fluid from the mixture of fattymaterials and the latent heat of vaporization of the fluid. In general,it is desirable to provide an absolute pressure of less than about 50mm. of mercury and preferably less than about 10 mm. of mercury.

Thereafter, a suitable fluid is evaporated in the presence of themixture. The fluid may be introduced into the mixture of fatty materialsprior to introduction of the mixture into the chamber or the fluid maybe introduced separately into the chamber while the chamber is undervacuum. It is preferred that the fluid have a latent heat ofvaporization of at least about 150 calories per gram at standardconditions of temperature and pressure and a boiling temperature atatmospheric pressure of less than about 200 C. A preferred fluid, forreasons of economy and availability, is water. However, other fluidshaving suitable evaporation and characteristics in terms of the latentheat of vaporization and atmospheric boiling temperature may be used solong as the fluid is substantially immiscible with and does not reactwith the fatty materials.

Preferably, a fluid is selected and vacuum conditions are establishedwhich permit the fluid to be evaporated at a rate sulficient to effect atemperature drop in the mixture of from about 25 F. to about 120 F. perhour. However, other rates of cooling are equally suitable. Evaporationof fluid is continued until the mixture is cooled to the desiredtemperature. The desired temperature is selected so that at least partof the mixture forms a solid phase. The mass or total weight of themixture of fatty materials which is to be cooled is not important. Therate of cooling depends on the rate at which fluid is evaporated perpound of mixture. Consequently, large volumes of fatty materials may berapidly cooled by the method of the invention. The described uniquemethod of cooling fatty material provides a solid phase with a crystalform which is readily adaptable to separation by filtration. If desired,filtration or separation of the mixture of organic compounds nowcontaining a solid phase and a liquid phase may be readily effectedwithout further treatment.

It has been found, however, that a higher degree of separation of theliquid phase of the mixture from the solid phase may be effected byfirst forming an emulsion with an aqueous solution of a surface activematerial. It is generally preferred to use levels of aqueous solution offrom about 50 to about 500 percent by weight of the mixture of fattymaterials. The emulsion may be effected by shaking, stirring or anyother manner assuring intimate contact between the mixture and theaqueous solution of a surface active material. During formation of theemulsion, the solid phase crystals are dispersed throughout theemulsion.

The surface active material reduces the interfacial tension between thesolid phase crystals and the aqueous medium. Surface active materialsare organic compounds which contain hydrophobic and hydrophilic groupsin the same molecule, usually separated by a long carbon chain. Theformation of an emulsion of the liquid phase of the mixture with theaqueous solution of the surface active material appears to tend tomaintain the liquid phase separate from the solid phase. Since theinterfacial tension between the solid phase and the aqueous emulsion hasbeen reduced, the solid phase is more easily separated therefrom. Inthis connection, however, the physical characteristics of the crystalsof the solid phase are important to effect a desirable separation, andit is important to effect cooling of the mixture of fatty materials toprovide solid phase crystals suitable for separation by the describedmethod.

Any known or conventional surface acting materials which are chemicallyinert with respect to the other components of the mixture of fattymaterials and which are water dispersible may be used. See, for example,those described in the publication Encyclopedia of Surface ActiveAgents, 1. P. Sisley and P. I. Wood, New York, 1952. Examples ofsuitable surface active materials include alkylphenolpolyglycol ether,alkylsulfonate, fatty alcohol sulfate and alkylbenzyl sulfonate.

The amount and concentration of the surface active material to be useddepends upon the properties of the surface active material and upon thelevel of aqueous phase used in forming the emulsion. Generally,concentrations of from about 0.05 percent to about 1.0 percent by weightof the mixture of fatty materials provides suitable results.

As previously described, the aqueous solution of the surface activematerial provides a wetting action which enables the aqueous phase towet the surface of the crystals of the solid phase and displace theliquid phase adhering thereto. In addition, the aqueous solution of asurface active material has an emulsifying property with respect to theliquid phase. It is desirable to limit the emulsifying action of theaqueous solution of a surface active material so as to provide anemulsification effect that is not so strong as to cause difficulty inthe subsequent separation of the liquid phase from the aqueous solution.The emulsifying properties of the solution of surface active materialcan be influenced by the addition of electrolytes which are inert to thefatty materials of the mixture. Electrolytes in the form of magnesium,calcium, aluminum or other soluble metal salts are suitable for thispurpose. A preferred electrolyte is magnesium sulfate. The concentrationof the electrolyte is dependent upon the property of the surface activematerial which is used. Generally, concentrations of electrolyte of fromabout 1.0 percent to about 7.0 percent by weight provides the desiredresult of limiting the emulsifying power of the surface active material.

As previously described, the cooling method of the described inventionprovides a solid phase of the higher melting components of the mixtureof fatty materials that are suitable for separation by conventionalsolidliquid techniques such as vacuum filtration or filter presses.

It will be appreciated by one skilled in the art that the conditions ofseparation, such as temperature, level of aqueous solution of surfaceactive material used, method of separation used, and other variableswill affect the properties of the liquid and the solid fatty materialthat are obtained.

When the temperature at which the separation is to be effected is belowabout 60 F., it is sometimes desirable to effect at least part of thecooling of the mixture of fatty materials by chilling the aqueoussolution of surface active material prior to introduction of the aqueoussolution into the mixture. Thus, after the mixture of fatty material iscooled by vacuum evaporation, as previously described, to a particulartemperature, the aqueous solution at a temperature below that to whichthe organic materials have been cooled is added and an equilibriumtemperature intermediate that of the mix ture of fatty materials and theaqueous solution is obtained. This method for further cooling of theorganic mixture may be desirable where refrigeration capabilities areavailable for effecting cooling of the aqueous solution of surfaceactive material.

Also, it may sometimes be desirable to effect at least part of thecooling of the mixture of fatty materials by circulating a cooling fluidin a jacket surrounding the chamber in which the fatty materials arecontained. This additional cooling may be desirable when the proportionof solid fatty materials is small in relation to the liquid fattymaterials.

The separation of the solid phase from the aqueous emulsion may beeffected in certain cases by allowing the mixture to stand andthereafter decantingthe layers of materials which form. In accordancewith a preferred embodiment of the invention, however, the aqueousemulsion is separated from the solid phase by vacuum or pressurefiltration. For this purpose, any suitable type of vacuum or pressurefiltering apparatus which is commercially available may be used.Centrifugal separation may also be used where the costs are notprohibitive.

The following examples are provided to further illustrate variousfeatures of the present invention, but are intended to in no way limitthe scope of the invention, which is defined in the appended claims.

EXAMPLE I One thousand grams of tallow fatty acids were heated to atemperature of 115 F. to provide a liquefied mixture of fatty acids. Thetallow fatty acids contained 49 percent saturated fatty acids and 51percent unsaturated fatty acids. The liquefied fatty acids at atemperature of 115 F. were introduced into a glass container equippedwith ports to permit drawing vacuum therein and to introduce a liquidwhile vacuum was maintained in the container. A vacuum of 6 mm. mercurypressure was drawn in the chamber. Water was then introduced into thecontainer through a port in the bottom of the container. The water wasadded at a level of 0.3 gram per gram of fatty acid over a period of 1.5hours. During this time period the temperature of the fatty acids wasreduced to 43 F.

One thousand grams of an aqueous solution containing 50 grams ofmagnesium sulfate and one gram of sodium lauryl sulfate was then addedto the container after the vacuum had been broken. The aqueous solutionhad been chilled to the same temperature as the fatty acids, i.e., 43 F.prior to introduction into the container. The Water was added slowlywith constant stirring to provide an emulsion. After the aqueoussolution had been added, the mixture was stirred for five minutes tocomplete wetting of the solid crystals of saturated fatty acids. Theemulsion, containing a dispersion of the solid crystals, was thentransferred to a Buchner funnel lined with coarse filter paper. Theaqueous emulsion containing the liquid unsaturated fatty acids was thenseparated from the solid crystals over a period of minutes, using avacuum of 15 inches. The aqueous emulsion broke immediately afterfiltration. The liquid phases obtained from the filtration step werethen allowed to set,.overnight in a steam bath. A liquid phase which Wasrich in oleic acid was then removed from the aqueous phase by means of aseparatory funnel.

The titer of the liquid oleic acid rich phase was then determined by theprocedure described in A.O.C.S. Method Tr-Ia-64. Titer is an arbitrarydesignation for the solidification temperature of a fatty material. Thetiter of the liquid oleic acid rich phase obtained by the method of theinvention was 2.5 C. The titer of commercially available oleic acid isnot usually lower than about 15 20 C.

EXAMPLE II One thousand grams of tallow fatty acids were heated to atemperature of 115 F. to provide a liquefied mixture of fatty acids. Thetallow fatty acids contained 49 percent saturated fatty acids and 51percent unsaturated fatty acids. The liquefied fatty acids at atemperature of 115 F. were introduced into a glass container equippedwith ports to permit drawing vacuum therein and to introduce a liquidwhile vacuum was maintained in the container. A vacuum of 6 mm. mercurypressure was drawn in the chamber. Water was then introduced into thecontainer through a port in the bottom of the container. The water wasadded at a level of 0.3 gram per gram of fatty acid over a period of 1.5hours. During this time period the temperature of the fatty acids wasreduced to 52 F.

One thousand grams of an aqueous solution containing 50 grams ofmagnesium sulfate and one gram of sodium lauryl sulfate was then addedto the container after the vacuum had been broken. The aqueous solutionhad been chilled to a temperature of 30 -F. prior to introduction intothe container. The equilibrium temperature of the mixture of fatty acidsand the water was 42 F. The water was added slowly with constantstirring to' provide an emulsion. After the aqueous solution had beenadded, the mixture was stirred for five minutes to complete wetting ofthe solid crystals of saturated fatty acids. The emulsion, containing adispersion of the solid crystals, was then transferred to a Buchnerfunnel lined with coarse filter paper. The aqueous emulsion containingthe liquid unsaturated fatty acids was then separated from the solidcrystals over a period of minutes, using a vacuum of 15 inches. Theaqueous emulsion broke immediately after tfiltration. The liquid phasesobtained from the filtration step were then allowed to set overnight ina steam bath. A liquid organic phase which was rich in oleic acid wasthen removed from the aqueous phase by means of a separatory funnel. Theliquid organic phase obtained had a titer of 2.5 C.

EXAMPLJE III Cottonseed oil was treated by the method of the inventionto effect winterization thereof. 900 grams of refined and bleachedcottonseed oil was heated to a temperature of F. and was held at thattemperature for a period of 30 minutes to insure the melting of thesolid saturated triglycerides. Thereafter, the cottonseed oil wastransferred to a chamber adapted for drawing vacuum and introducing aliquid thereto while the vacuum was being held. The chamber was alsoprovided with a jacket through which a cooling fluid could becirculated. The cottonseed oil was then cooled to a temperature of 45 F.over a period of 30 minutes while being slowly stirred by circulatingchilled water through the jacket. At this temperature a slight haze wasobserved in the cottonseed oil. A vacuum of 10 millimeters of mercurywas then drawn. Water was then bubbled into the chamber from the bottomover a period of 7 hours at a rate of 0.3 gram of water per gram ofcottonseed oil. The temperature of the cottonseed oil was reduced to 40F. 30 inches of vacuum was maintained at a temperature of 40 F. by thecontinued vacuum evaporation of the water. The vacuum was then brokenand an aqueous solution was slowly introduced into the chamber while thecottonseed oil was continuously stirred. The aqueous solution contained900 grams of water, 1.8 grams of sodium lauryl sulfate and 45 grams ofmagnesium sulfate. The water had been previously chilled to atemperature of 40 F. and the temperature of the mixture was maintainedat 40 F.

After the water had been added, the mixture was stirred for two minutesto form a loose emulsion of the water with the liquid phase of the oiland containing a dispersion of the solid crystals therein. The emulsionwas then transferred to a Bnchner funnel located in a room maintained ata temperature of 45 F. and the solid phase was separated therefrom.

The liquid cottonseed oil was then recovered from the emulsion by themethod described in Example I. The yield was 83 percent by weight of thestarting oil and the liquid. cottonseed oil obtained had a cold test of132 hours. This compares with a yield of about 65 percent and a coldtest of about hours obtained when winterization is effected byconventional vat cooling.

Various of the features of the invention are defined in the appendedclaims.

It is claimed that:

1. A method for the separation of a mixture of fatty materials intofractions wherein the components of the mixture have different meltingpoints which method comprises, providing a mixture of fatty materials inat least a partially melted state, treating the mixture so as to lowerthe temperature to a level wherein at least part of the mixture issolid, said temperature also being such that at least part of themixture remains liquid, said lowering of temperature being effected byproviding a lower boiling fluid in said mixture and subjecting themixture and fluid to vacuum conditions so as to evaporate said fluidfrom said mixture thereby cooling said mixture, adding to said cooledmixture an aqueous solution containing a surface active material,forming an emulsion of said aqueous solution with said liquid portion ofsaid cooled mixture, and thereafter separating said emulsion into aliquid phase and a solid phase.

2. A method in accordance with claim 1 wherein said fluid which is to beevaporated is added to said mixture of fatty materials prior tosubjecting said mixture to vacuum.

3. A method in accordance with claim 11 wherein said fluid which is tobe evaporated is added incrementally to said mixture of fatty materialsafter said mixture is subjected to vacuum conditions.

4. A method in accordance with claim 1 wherein said surface activematerial has at least one hydrophilic group and at least one hydrophobicgroup.

5. A method in accordance with claim 1 wherein said surface activematerial is present at a level of at least 0.05 percent by weight ofsaid fatty materials and wherein said aqueous solution is present at alevel of from about percent to about 500 percent by weight of said fattymaterials.

6. A method in accordance with claim 1 wherein said aqueous solution ofa surface active material also contains an electrolyte.

7. A method in acordance with claim 6 wherein said electrolyte ispresent at a level of from about 1.0 to about 7.0 percent by weight ofsaid aqueous solution.

8. A method in accordance with claim 1 wherein said vacuum condition isestablished at an absolute pressure of 50 millimeters of mercury or lessand wherein said fluid is evaporated from said container at a levelsufficient to cool said mixture of fatty material at a rate of fromabout 25 F. to about F. per hour.

9. A method in accordance with claim 1 wherein said mixture of fattymaterials is selected from saturated and unsaturated fatty acids.

10. A method in accordance with claim 1 wherein said fluid which is tobe evaporated has a latent heat of vaporization of at least aboutcalories per gram at standard conditions of temperature and pressure.

11. A method in accordance with claim 1 wherein said fluid which is tobe evaporated has a boiling temperature at atmospheric pressure of lessthan about 200 C.

12. A method in accordance with claim 1 wherein said fluid which is tobe evaporated is water.

13. A method in accordance with claim 1 wherein said aqueous solution iscooled prior to adding to said cooled mixture.

14. A method in accordance with claim 1 wherein said mixture of fattymaterials is at least partially cooled by heat transfer between saidmixture of fatty materials and a cooler fluid material.

References Cited FOREIGN PATENTS 165,094 3/1954 Australia. 658,96710/1951 Great Britain.

LEWIS GOTTS, Primary Examiner.

E. G. LOVE, Assitant Examiner.

U.S. Cl. X.R. 260428

